A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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9 views

extracting t value out of pairwise.t.test [migrated]

I would like to know if I could extract t values out of the pairwise.t.test function since it is only reporting the p values. I used the pairwise.t.test() for multiple comparisons after running a ...
-5
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2answers
51 views

This is purported to be a paired t-test - I doubt it [on hold]

This is the problem: Some nerve cells have the ability to regenerate. Researchers think that these cells may generate creatine phosphate (CP) to stimulate new cell growth. To test this ...
3
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0answers
21 views

How to compare three groups to one control group without assuming equal variances?

I need to determine if one dependent variable (tensile strength) for each of three new groups is equivalent to that from my original ("control") group. I am not concerned with how the three new groups ...
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1answer
27 views

Comparison of two means within the same group

I created a pretest before my main study. The goal of the pretest is to find two brands that are equal in terms of liking and familiarity. I computed the variables in SPSS and I was wondering if I ...
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0answers
33 views

Compare more than two means

New in statistics and I need your help regarding an easy question I think. I'm running out of time for my assignment so I kindly ask you to help me if possible. I'm running a pretest and the main ...
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0answers
23 views

Mann Whitney or t test?

I have 4 questions which ask different branches of the same topic (I suppose they are related to each other). Different numbers of people responded to each question. They responded to each question by ...
2
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2answers
26 views

When to create a control group with paired T test

So if I wanted to measure the effect of a drug on a group of people, I think I would use a paired T test based on my research. But what if something caused a change in my group that I did not account ...
3
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0answers
18 views

Is the increase in Type I errors due to multi-sample t-tests overstated?

To illustrate, let's say you want to compare the means of 3 samples with t-tests. You would then have to run 3 tests to compare the means of each possible combination of samples. The explanations I ...
3
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1answer
35 views

Statistics on tastings

Some people at my workplace have had some fun lunch discussion as of late, concerning some people's alleged ability to taste the difference between things one thought one shouldn't be able to taste a ...
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3answers
34 views

How can I run a t.test in this situation of two processes having binary outcomes

I have two processes, lets call them A and B. I want to infer whether their population means are equal for their experimental outcomes. Both of these processes generate 1s and 0s only. That is, the ...
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1answer
52 views

Self Selection bias for estimating a valiable correlated to the selector

I am trying to find a way to see if a measured variable between two groups is significantly different. This would normally be done through a t-test if the two groups were randomly selected from the ...
2
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1answer
43 views

Manually calculating p-value for t-test: How to avoid values bigger $1$?

These two methods for calculating the p-value should be equivalent: t.test(rats.drug,mu=1.2)$p.value 2*pt((mean(rats.drug)-1.2)*sqrt(n)/sd(rats.drug),df=n-1) The ...
2
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1answer
160 views

Why is the difference between these two t-tests so big?

I am using a t-test to find out whether the mean of a sample ($1.05$) with a sample size of $100$ is significantly different from a given mean ($1.2$). The standard deviation should be $0.5$: ...
1
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1answer
35 views

paired t-tests and interpretation of results

My study is about comparing the scores a group of students (sample, N=14) in two different conditions. They play the same game in a tablet and using a computer. They were administered with a ...
5
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1answer
174 views

Is using error bars for means in a within-subjects study wrong?

I seem to recall one of my professors saying that error bars are completely uninformative when comparing repeated measures taken from a single group. Is that true? Surely many studies compute the ...
4
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2answers
124 views

Alternative to T-Test

I have a series of values and I need to test if the returns are > 0. The t-test assumes normality, so I was wondering if there are other alternatives. Note that the standard suggested sample size is ...
2
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0answers
25 views

Equivalence of intercept beta test to one-sample t-test in linear regression model with categorical variable

I am testing my understanding of the equivalence between basic linear regression with categorical variables, and one-sample / independent samples t-tests. I don't think this corresponds to an existing ...
-1
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0answers
39 views

Comparing two dataset using several different tests

I have several datasets of about 10k items. I have to compare all of them with the reference dataset, and draw some conclusions as to which is the best. Let's say I have no information on the shape ...
2
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1answer
24 views

T-test table interpretation error?

For a research project I have obtained results which I have to test for significancy. The two values I am comparing are the true diameter of a certain object versus the calculated diameter of that ...
4
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2answers
123 views

Timing attacks: When the time to complete two different tasks are statistically indistinguishable

This question is related to the open source security package for node/Javascript called credentials, and in particular how to evaluate whether a comparison of two strings is "constant time", though ...
3
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1answer
77 views

Would a one-tailed t-test technically be considered Bayesian?

I'm just curious whether the expectation implied from a one-tailed test would somehow be considered a prior, and whether this is enough for it to be in the purview of Bayesian statistics.
3
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3answers
112 views

Which statistical test to use when comparing two ratios?

I have five independent experiments. In each experiment I record the intensity of sample A and sample B, then add these intensities together and calculate A and B as a proportion of the total. ...
1
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1answer
37 views

Running tests over samples from cross-validation on multiple datasets. To average or not to average?

Let us say that I am trying to investigate whether we can reliably decode (i.e., predict) some information from some data. The particular scenario is predicting the object a person is seeing from the ...
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1answer
42 views

Is it justified to use a one-tailed t-test if I my hypothesis is one-sided?

I am looking to see if the mean of group A is higher than the mean of group B using an unpaired t-test. I don't really care if group B is lower than group A (it might actually mean something, but it ...
2
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0answers
22 views

T-test for a small sample with unknown distribution [duplicate]

Consider a simple hypothesis test concerning the mean of a single sample. If the sample is normally distributed and the variance is known, the exact distribution of the sample mean is known ...
2
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2answers
43 views

Stats t-test for soccer data

I am new to stats and had the following question I am studying if the total number of fouls in a soccer game increases/decreases if a particular team is winning at half time. This is what I did (one ...
4
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4answers
196 views

Both t-test and F-test are significant, do I report both?

I undertook a large study (N about 200 in both control and treatment) in which one of the user ratings is significantly different (p < 0.0001). When I ran the unpaired t-test, the F-test also ...
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0answers
16 views

If I perform multiple unpaired t-tests on data, then break it down by gender, do I need to do additional multiple correction?

I have data from a treatment and control group, I'm performing ~7 unpaired t-tests. I had pre-planned to look at differences between genders too. Now I am doing another set of t-tests within females ...
2
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2answers
153 views

If I ran 10+ unpaired t-tests, do I report them all?

1) Should I be reporting the results of all the t-tests I ran, or can I just talk about the ones that were significant? 2) Must I report the t-statistic, df, effect size in all cases? I am pressed ...
2
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0answers
25 views

Paired or not paired? Comparing groups after propensity score matching

After matching on propensity score, e.g 1:1 matching, you obtain a matched subset of your data. The built-in functions in the Matching package, as a prominent example, compares groups before matching ...
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2answers
29 views

Paired T test vs 2 sample t test

I have been given data that includes 20 different households and what each household spends on grocery and restaurant. I need to run a t test and I'm not sure if I should use a paired t test or a 2 ...
1
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2answers
38 views

What test to compare three groups with data before and after an intervention?

I am writing a proposal for a study. I have 3 groups: Group A- receiving specialized intervention technique Group B- receiving regular intervention Group C- control/receiving no intervention I ...
2
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1answer
49 views

Why would I want to bootstrap when computing an independent sample t-test? (how to justify, interpret, and report a bootstrapped t-test)

Let's say I have two conditions, and my sample size for the two conditions is extremely low. Let's say I only have 14 observations in the first condition and 11 in the other. I want to use the t-test ...
3
votes
1answer
50 views

p-value correction for multiple t-tests?

My dataset consists of $n$ genes, each of them described by a vector of expression values, $5$ for "healthy" individuals, and $5$ for "unhealthy" individuals. I am going to run $n$ t-tests (one for ...
3
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0answers
25 views

chi-squared test vs fisher's test vs … => highly unbalanced length frequency data

I would like to statistically verify if two distributions are identical. Basically, the first distribution is a length frequency distribution from a large population ("population"). The second is the ...
2
votes
3answers
164 views

Bootstrap two-sample t test

I'd like to bootstrap a two sample t-test. My DV is some psychological variable. I have two groups (women and men), unequal sizes and I do not assume equal variances. I'm not sure if my code or/and my ...
0
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1answer
13 views

Is it valid to run unpaired t-tests with large N in one condition and small N in the other?

Basically, I have collected sets of data from two demographic groups. One of my demographic groups (say, Male) I have lots and lots of data (N=182). In my other demographic group (say, Female) I have ...
4
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4answers
120 views

Paired t-test when each data point was repeatedly measured different number of times?

I have an existing data set that comes from the same group of people before and after they received a treatment. The data set comes from when participants tested their blood sugar values over a 30 ...
1
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1answer
35 views

Is this a right way to use paired t-test

Problem Description I want to enhance a photo and I have 3 software to do that, out of which 2 are my own. I show users 2 photos and ask them to choose a better one. Now, I compare software 1 vs. 2, ...
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0answers
25 views

Appropriate Test of Significance for Eye Tracking Data

Hello my clever friends, I conducted an eye-tracking study and now I'm in statistical hot water. Given the characteristics of the data, I am not sure which test of significance to apply to answer the ...
3
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7answers
339 views

How to judge if 5 point Likert scale data are normally distributed?

I have read that the t-test is used when the population is normally distributed. How can I determine if my data are normal given that I am using 5-point Likert scale with a sample size of 100? What ...
1
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1answer
17 views

Mean comparison of two categorical variables

I'd like to compare people's perception of safety at a certain location [which is a categorical variable on a scale of 1-10, with 1=feel very unsafe & 10=feel very safe] before and after being ...
2
votes
1answer
50 views

How can I test and quantify the change in distribution over multiple years?

I have a data set of energy usage values taken every half hour for a year, for four years. How can I test for, and quantify, an improvement (i.e. decrease) in energy usage, per-year? I have initially ...
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0answers
20 views

What analysis should I run?

For an RCT, I want to test scores on BES(Binge Eating Scale) and BMI over time for two different groups(experimental and control group)to register whether treatment had an effect on reducing symptoms ...
0
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1answer
34 views

Compare two distributions of large sizes and unequal variances where one distribution is heavily skewed

My data is from cells that are treated under two different conditions and then their response to the condition is measured by one output variable. The cell populations in the two conditions are quite ...
1
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1answer
35 views

T-test or ANOVA

I have 4 groups. I would like to compare the effect of 3 different treatments relating to drug treatment of a sample individually against a single control sample. Control (no drug) Treatment A (low ...
0
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2answers
59 views

How do I obtain a t distribution?

I performed an independent groups t-test and got a t value of 4.48. Each group is of 26 and I used a criterion of 0.05 (just because...). Before doing the t-test I had to transform my values because ...
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0answers
36 views

When do we have to standardize/normalize data?

I have to perform an independent group t-test and have unequal variances. From what I understand, the solution is to transform the data. To transform it, do I standardize it? Or simple use log10 to ...
2
votes
1answer
44 views

Which statistical test should I use to compare two samples?

I have two groups and must conduct hypothesis testing by using an appropriate stats test. Seeing as I have 26 participants in each group, do not have the standard deviation (or any other information ...
2
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1answer
36 views

Do I have to standardize my data to calculate variance?

I have 2 groups/samples. Correct me if I'm wrong, but before doing an independent-group t-test we have to verify the homogeneity of variance with Hartley's F-max test. When doing this test, we have ...